1. Field of the Invention
The present invention relates generally to a steering control mechanism for a personal watercraft (xe2x80x9cPWCxe2x80x9d). More specifically, the invention concerns a control system that assists in steering a PWC when the jet pump pressure falls below a predetermined threshold.
2. Description of Related Art
Typically, PWCs are propelled by a jet propulsion system that directs a flow of water through a nozzle (or venturi) at the rear of the craft. The nozzle is mounted on the rear of the craft and pivots such that the flow of water may be directed between the port and starboard sides within a predetermined range of motion. The direction of the nozzle is controlled from the helm of the PWC, which is controlled by the PWC user. For example, when the user chooses to make a starboard-side turn, he turns the helm to clockwise. This causes the nozzle to be directed to the starboard side of the PWC so that the flow of water will effect a starboard turn. In the conventional PWC, the flow of water from the nozzle is primarily used to turn the watercraft.
When the user stops applying the throttle, the motor speed (measured in revolutions per minute or RPMs) drops, slowing or stopping the flow of water through the nozzle at the rear of the watercraft and, therefore, reducing the water pressure in the nozzle. This is known as an xe2x80x9coff-throttlexe2x80x9d situation. Pump pressure will also be reduced if the user stops the engine by pulling the safety lanyard or pressing the engine kill switch. The same thing would occur in cases of engine failure (i.e., no fuel, ignition problems, etc.) and jet pump failure (i.e., rotor or intake jam, cavitation, etc.). These are known as xe2x80x9coff-powerxe2x80x9d situations. For simplicity, throughout this application, the term xe2x80x9coff-powerxe2x80x9d will also include xe2x80x9coff-throttlexe2x80x9d situations, since both situations have a similar effect on pump pressure.
Since the jet flow of water causes the vehicle to turn, when the flow is slowed or stopped, steering becomes less effective. As a result, a need has developed to improve the steerability of PWCs under circumstances where the pump pressure has decreased below a predetermined threshold.
One example of a prior art system is shown in U.S. Pat. No. 3,159,134 to Winnen, which provides a system where vertical flaps are positioned at the rear of the watercraft on either side of the hull. In this system, when travelling at slow speeds, where the jet flow through the propulsion system provides minimal steering for the watercraft, the side flaps pivot with a flap bar into the water flow to improve steering control.
A system similar to Winnen is schematically represented by FIG. 25, which shows a watercraft 1100 having a helm 1114. Flaps 1116a, 1116b are attached to the sides of the hull via flap bar 1128a, 1128b at a front edge. Two telescoping linking elements 1150a, 1150b are attached to arms 1151a and 1151b, respectively, at one end and to the respective flap bars 1128a, 1128b at the other end, respectively. Arms 1151a, 1151b, are attached to partially toothed gears 1152a, 1152b, respectively. Gear 1160 is positioned between gears 1152a, and 1152b to engage them. Gear 1160 is itself operated, through linking element 1165 and steering vane 1170, by helm 1114. FIG. 25 illustrates the operation of the flaps when the watercraft is turning to the right, or starboard, direction.
Because the gears 1152a, 1152b are only partially toothed, when attempting a starboard turn, only gear 1152b will be engaged by gear 1160. Therefore, the left flap 1116a does not move but, rather, stays in a parallel position to the outer surface of the hull of the PWC 1100. Thus, in this configuration, the right flap 1116b is the only flap in an operating position to assist in the steering of the watercraft 1100.
While the steering system of Winnen, represented in FIG. 25, provides improved steering control, the system suffers from certain deficiencies. First, steering is difficult. When the flap bars 1128 are located at the front portion of the flaps 1116 (as shown), the user must expend considerable effort to force the flaps 1116a, 1116b out into the flow of water. Second, the force needed to force flaps 1116a, 1116b into the water stream causes considerable stress to be applied to the internal steering cable system that may cause the cable system to weaken to the point of failure. Third, only one flap 1116b is used at any given moment to assist in low speed steering. Thus, the steering system shown in FIG. 25 is difficult to use, applies unacceptable stresses to the internal steering system, and relies on only half of the steering flaps to effectuate a low speed turn.
Such a system could be modified to use simpler telescoping linking elements to attach the steering vane 1170 to flaps 1116, instead of the more complex gear arrangement. Unfortunately, the sliding nature of the telescoping linking elements makes these structures susceptible to seizing up in salt water.
For at least these reasons, a need has developed for an off-power steering system that is more effective in steering a PWC when the pump pressure has fallen below a predetermined threshold.
A PWC according to this invention has an improved system comprising at least one flap or rudder placed at a side of the hull. This invention relates to the design and operation of generally vertical rudders positioned on the port and starboard sides of the PWC hull that assist in steering the PWC when the pump pressure falls below the predetermined threshold. In addition, the rudders can be vertically adjustable to provide even greater assistance in steering control when the pump pressure falls below the predetermined threshold.
Therefore, one aspect of embodiments of this invention provides an off-power steering system in which the rudders and linking elements assist the driver in steering a PWC in off-power situations without causing undue stress on the driver or the helm control steering mechanisms.
Another aspect of the present invention provides a PWC with simplified linking elements that do not seize up in salt water, and are less complex than those known in the prior art.
An additional aspect of the present invention provides an off-power steering mechanism that automatically raises and lowers vertical rudders according to the water flow pressure within the venturi or flow nozzle.
A further aspect of the present invention can make off-power steering more efficient by using both rudders simultaneously and in tandem to assist in steering.
Embodiments of the present invention also provide an improved rudder that can be used with an off-power steering system.
An additional embodiment of the present invention provides an off-power steering mechanism kit to retrofit a PWC that was not manufactured with such a mechanism.
These and other aspects of the present invention will become apparent to those skilled in the art upon reading the following disclosure. The present invention preferably provides a rudder system wherein a rudder is positioned near the stern and on each side of the hull of a PWC. The preferred embodiment utilizes a pair of vertically movable rudders operating in tandem during steering.
The invention can provide a steering system that is simpler to build and easier to steer. The system can automatically lower the vertical rudders when off-power steering is necessary and can automatically raise the vertical rudders when off-power steering is not needed.
The rudders according to this invention are spaced a predetermined distance from the hull and pivot from a position inwardly from an edge of the rudder to enable water to flow on an inside surface and an outside surface. Other embodiments of the invention are described below.
It is contemplated that a number of equivalent structures may be used to provide the system and functionality described herein. It would be readily apparent to one of ordinary skill in the art to modify this invention, especially in view of other sources of information, to arrive at such equivalent structures.